1. Field of the Invention
The present invention generally relates to an image projection apparatus and method, and more particularly to an image projection apparatus and method for amplifying light quantity by using a fluorescent material. The present application is based on Korean Application No. 2001-78491, filed on Dec. 12, 2001, which is incorporated herein by reference.
2. Description of the Prior Art
Generally, display apparatuses such as projectors and projection systems display images by converting lights from a light source into image signals and projecting the converted signals to a screen. Electromagnetic waves such as radio waves and microwaves are generally used in the display apparatuses.
The electromagnetic waves include not only ultraviolet rays, visible rays and infrared rays, but also include electro waves, for transmitting signals through radios or TVs, and X-rays. The electromagnetic waves are characterized by frequency and wavelength.
Optics usually uses visible rays, and sometimes uses ultraviolet rays, infrared rays and X-rays.
Visible rays are perceptible by the human eye, and have a wavelength ranging from 400 nm (violet) through 700 nm (red). The visible rays vary in color according to their wavelength. For example, the monochromatic light is divided into red in the wavelength range of 610 nm through 700 nm, orange in 590 nm through 610 nm, yellow in 570 nm through 590 nm, green in 500 nm through 570 nm, blue in 450 nm through 500 nm, and purple in 400 nm through 450 nm.
Ultraviolet rays have a wavelength of 10 nm through 400 nm, and the infrared rays have a wavelength of 0.7 nm through 1 nm.
An object emits a light when exposed to an ultraviolet ray, X-ray or electron ray, and such a light emission is called a luminescence. Fluorescence and phosphorescence are types of luminescence. The fluorescence is visible rays of different colors reflected from a certain non-heated object in response to an external stimulus. The non-heated material is called a fluorescent material. The fluorescent material may be applied in a fluorescent lamp, neon and cathode-ray tube.
For example, the fluorescent lamp glows by using a fluorescent material and electricity. An electric field stimulates mercury and electron vapor by an electric discharge between two electrodes, thereby generating ultraviolet rays. The ultraviolet rays pass through the fluorescent material, and thus are converted to the visible rays perceptible by the human eye. As a result, the fluorescent lamp glows.
FIG. 1 is a view showing the basic structure of a conventional image projection apparatus using a color wheel, and FIG. 2 is a view showing the distribution of spectrum energy of the white light radiated from the conventional light source.
Referring to FIG. 1, the conventional image projection apparatus 100 using a color wheel includes a light source 110, a color wheel 120, a digital micromirror device (DMD) panel 130 and a projection lens 140. The phantom line in FIG. 1 indicates the light path of the white light.
The light source 110 irradiates white light by using an arc lamp or a laser beam. The color wheel 120 is rotated by a rotary means (in the arrowed direction), and is divided into red (R), green (G) and blue (B) regions. White light from the light source 110 is divided into RGB beams according to the RGB regions of the color wheel 120.
The DMD panel 130 includes a plurality of micromirrors 130a. RGB beams divided by the wavelengths are passed through the DMD panel 130 and reflected from the micromirrors 130a. After being reflected, each of the RGB beams passes through the projection lens 140 and is realized on the screen as an image.
The light source 110 used in the conventional image projection apparatus 100 uses white light that usually includes RGB beams. Referring to FIG. 2, the horizontal axis indicates the distribution of wavelengths, while the vertical axis indicates the distribution of spectrum energy. The white light includes visible rays (RGB beams) and ultraviolet (UV) rays.
While the visible rays are used in realizing images, the ultraviolet rays vanish. In the visible light that includes the RGB beams, the R and B beams, and more particularly the R beam, have a lesser light quantity when compared to the G beam.
Because the light quantity of the R beam is considerably lacking in the conventional image projection apparatus, the images formed on the screen usually have a deteriorated color purity and brightness. Further, as the ultraviolet rays vanish, the R beam remaining in the ultraviolet ray also vanishes.
Accordingly, it is an aspect of the present invention to provide an image projection apparatus and method capable of amplifying a light quantity of white light by fluorescing lights other than the visible rays irradiated from a light source.
The above aspect is accomplished by an image projection apparatus according to the present invention, including a light source for irradiating a white light; a light quantity amplifying unit for amplifying the light quantity of a ray of the white light having a certain wavelength, and outputting the amplified ray; a light separating unit for receiving the white light from the light quantity amplifying unit and separating the received light into plural monochromatic lights; and a digital micromirror device (DMD) panel for reflecting the monochromatic lights at a predetermined angle.
The light quantity amplifying unit is comprised of a fluorescent material that transforms the white light into light of a certain wavelength by letting the wavelength of the visible light band pass, while absorbing the other wavelengths. The light quantity amplifying unit moves an intermediate wavelength of the certain wavelength within a predetermined range.
The light separating unit is comprised of a rotatable wheel that is divided into red, green and blue regions, for separating the white light into the plural monochromatic lights. Further, a square beam generating unit is provided for transforming the monochromatic lights, received from the light separating unit, into a square beam.
Additionally, it is an aspect of the present invention to provide an image projection method for realizing an image by irradiating a white light. A light quantity of a ray of the white light having a certain wavelength is amplified, wherein the white light is separated into a plurality of monochromatic lights. The monochromatic lights being reflected at a predetermined angle, wherein a projected image is realized.
According to the present invention, it is possible to enhance the light utilization efficiency by amplifying the light quantity of the light, especially of the R or B band, which has the wavelength corresponding to that of the visible light band.